Ulster Bank's senior managers are to be hauled before the Finance Committee to explain why there are so many collapses of its electronic payments system.

It comes after the bank again suffered a systems breakdown that meant customers could not access its online and mobile banking services.

The breakdown happened on a day when many workers were due to be paid.

The bank's customers have suffered repeated problems trying to access their money due to countless IT problems in the past number of years.

Chairman of the Finance Committee John McGuinness said the bank had been written to in a bid to get its new chief executive Jane Howard to explain to politicians why there are so many problems with its IT systems.

The Fianna Fáil TD said: "We asked them to come in to the committee before but they said at the time the breakdown was due to a human error. Now it has happened again. There is a bigger issue. It is either a human error or an IT issue, but it is not good enough for customers."

Committee member Pearse Doherty, of Sinn Féin, said: "There is a clear pattern of IT failures now. It is unacceptable."

The bank, which has battled with numerous IT problems in recent years, apologised to customers for the service outage and said that no one would be left out of pocket as a result.

It insisted the latest outage was not the result of a cyber attack, but due to an update of the system that was made the night before the IT meltdown.

Ulster Bank was previously fined €3.5m by the Central Bank in 2014 for IT failures that affected 600,000 customers between June and July 2012. The bank also paid out €59m under a redress scheme for customers affected by the 2012 IT failures.

Earlier this year, Ulster Bank had to promise customers emergency cash of up to €500 after money disappeared from accounts due to technical issues. Asked why there were so many system collapses, the bank insisted it was investing heavily in its IT infrastructure. It confirmed that its system was linked into that of its sister bank in the UK, NatWest.

This is despite repeated calls for a separation of the two IT systems.